The present invention relates to in-dwelling ureteral catheter stents and to the method of using the same.
In-dwelling ureteral catheter stents or drainage tubes have been used to bypass ureteral obstructions or uretero-vaginal fistulas and maintain urinary drainage. Stents made of straight lengths of open-ended tubing are widely used for this purpose and have provided drainage for sustained periods of time. However, the use of such open-ended tubing has not been completely satisfactory in that, in some instances, the tubing has migrated, and, in other cases, it has been expelled.
To combat the problem of migration or expulsion, stents have been designed which are closed at the proximal end to facilitate passage into the ureter, and which have a flange or other formation at the distal end to preclude upward migration of the stent. U.S. Pat. Nos. 4,212,304 and 4,307,723 disclose ureteral stents with ends having portions with hooks or curls which have been effective in preventing migration and expulsion. Such stents can be introduced both endoscopically and during open surgery.
Other stents having formed proximal and distal ends to combat migration and expulsion are disclosed in U.S. Pat. Nos. 4,643,716; 4,610,657; and 4,713,049.
At the present time, there are two general types of ureteral stents available. One type is made of a soft material, and the other is made of a stiff material. Each requires a different method of placement within the ureter and each has its advantages and disadvantages. A ureteral stent made from a soft material has a closed proximal tip which is inserted into the kidney. This type of stent is placed in the ureter by inserting a stiff stylet through the distal end until it abuts against the proximal tip. The stent stiffened by the stylet is guided into the bladder with the use of a standard cystoscope. Once the ureteral orifice is located, the stent is advanced up the ureter by pushing the stylet against the closed proximal end.
The disadvantage of using a stent of soft material is that it must be stiffened and guided by a stylet. This increases the possibility for the stent to migrate and perforate the ureteral wall, especially if the ureter is partially obstructed or tortuous. After placement, soft stents have a greater tendency to migrate distally and proximally because soft curls formed therein will straighten easily.
A ureteral stent made from a stiff material has open distal and proximal ends. The stent is inserted by first inserting the guide wire through the ureter into the kidney and the stent is fed over the guide wire which straightens its curls as it travels thereover. A push rod is slid over the guide wire until it abuts the distal end of the stent. Because the material is stiff, this stent may be advanced along the guide wire with the push rod without collapsing the stent and with less chance of perforating the ureteral wall. Once the stent is in place, both the push rod and guide wire are removed and the distal and proximal ends curl to prevent the stent from migrating or being expelled. The major disadvantage of using the stiff material stent is patient discomfort, because the distal curl tends to irritate the bladder wall when the bladder is empty.
With the development of the extracorporeal shockwave lithotriptor (ESWL) which provides a non-invasive method of breaking kidney stones using shock waves, the use of stents has greatly increased, and most patients with large kidney stones are stented prior to ESWL procedures. This is to aid in the migration of sediment from the kidney to the bladder as well as to prevent the possible formation of steinstrasse (stone street) which occur when a large fragment of the disintegrated stone blocks the ureter. By stenting a patient prior to ESWL, large fragments cannot enter the ureter and cause urinary blockage.
It is an object of the present invention to provide a new and improved in-dwelling ureteral stent with curled end portions for anchoring the stent in the kidney and bladder.
It is also an object to provide such a stent which affords greater comfort to the patient.
Another object is to provide a catheter assembly permitting facile and accurate placement of the stent and facilitating irrigation of the kidney.
A further objection is to provide an improved method for placement of a ureteral stent and irrigating the kidney.